Genetic Analyses of Heat-Sensitve Pawn Mutants of PARAMECIUM AURELIA.

Heat-sensitive Pawn (ts Pawns) of Paramecium aurelia behaved normally when grown at 23 degrees but failed to avoid strong stimuli at 35 degrees . Four of the five ts Pawn lines tested were found to be allelic at a locus known also to carry temperature-independent Pawn mutations. The fifth ts Pawn line complemented all the conditional and unconditional Pawn mutants of the two known loci. This result, together with the patterns of F(2) segregation from various crosses, suggested the existence of a third Pawn locus. An additive effect of the unlinked ts Pawn genes was observed. These findings and the significance of ts Pawns as experimental material in behavioral and physiological research are discussed.